In this picture the young Crassula rupestris flower with yellow anthers and short stigmas on the right can be compared to the older one below: The older flower’s anthers are by now without pollen and the stigmas on top of the separate carpels in the flower centre tall and brown-tipped.
Imported pollen has probably already reached the stigmas from other flowers, events only supposed to happen after the local stamens had run out of stock. The ovaries in a ring of separate carpels in the older flower have also grown bigger, vital improvements aimed at their imminent fruit production activities.
Further buds are ready to follow the same blooming cycle, carried upon sturdy looking pedicels fashioned to last until seed dispersal time (Vlok and Schutte-Vlok, 2015; iNaturalist).